/*
 * Copyright 2021 4Paradigm
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com._4paradigm.openmldb.batch.utils

class AutoDestructibleIterator[T](iter: Iterator[T], destructor: => Unit) extends Iterator[T] {

  private var _destructed = false

  override def hasNext: Boolean = {
    val flag = iter.hasNext
    if (!flag && !_destructed) {
      destructor
      _destructed = true
    }
    flag
  }

  override def next(): T = {
    iter.next()
  }
}

object AutoDestructibleIterator {
  def apply[T](iter: Iterator[T])(destructor: => Unit): AutoDestructibleIterator[T] = {
    new AutoDestructibleIterator[T](iter, destructor)
  }
}

